Sirens commonly in use on emergency vehicles are of several types, i.e., as one utilizing a slowly rising and falling sound with a single or repetitive cycle, one using an alternating high and low frequency of sound or one using a slowly rising and falling sound frequency with minor sound frequency variations occurring during each cycle of the rising and falling sound. In the latter class of sirens, the sound has been produced by mechanical means. The first two types of sound producing sirens have heretofore been reproduced mechanically and electronically through use of motors or electrical amplifiers but, as far as is known, the third class has not heretofore been produced electronically. The mechanically produced siren noise has some desirable qualities not found in electronically produced siren sounds which may be attributed to purely mechanical noises resulting from the sound producing apparatus. Mechanically driven baffling is used with mechanical sirens to create a minor pulsing of the siren sound during each cycle of rising and falling frequency of the sound.